1. Field of the Invention
This invention relates to an image formation apparatus, such as, an electronic copying machine, provided with a selective sheet sorting function.
2. Description of the Related Art
Electronic copying machines of known construction include those comprising a copying device, an automatic original feeder and a sorting device.
The copying device of such a machine comprises an original placement plate for carrying an original to be copied, an image formation unit for forming an image corresponding to the image information of the original on sheet material, and discharge rollers for discharging the imaged sheet material externally of the device.
The automatic original feeder is generally provided with an original feeder plate on which originals to be copied are supplied, an original delivery and discharge unit which deliver the originals from the original feeder plate to the original placement plate and discharges them out of the original placement plate, and an original discharge bins or trays for receiving the originals discharged by the delivery and discharge unit.
The sorter device includes a vertically movable support frame, a plurality of bins or trays positioned vertically along with support frame, and a pair of feed rollers which transport sheet material discharged by the copying device via a pair of discharge rollers to a selected one of bins. A sorter device of this type is disclosed in U.S. Pat. No. 4,618,245.
In the sorter device of the above known arrangement, all bins conjointly perform upward and downward movements. During the course of the movements, each bin faces feed rollers in turn, whereby imaged sheet material is sorted in each bin. This requires all of the sheets carried by different bins to be moved upward or downward in line with the movement of bins, with the result that a large actuation power is necessary for the movement of the bins.
In automatic original feeder devices of a known construction, an original to be copied is fed to the original feeder plate with its image carrying surface facing downward. The original is sent to the original placement plate and discharged to the original receiving bins with its image carrying surface retained to face downward. An original subsequently fed is treated in the same manner and placed on the preceding one after a copying cycle. With the copying device, on the other hand, an image is formed on the upper surface of sheet material and the sheet is discharged with its imaged surface facing upward. In the sorting device, the sheet material is received by a bin with its imaged surface facing upward. Subsequently fed sheets of paper are received by the bins and placed on preceding ones in a like fashion. The above arrangements cause the order of pages of accumulated originals and that of the sheet material to be reversed. This provides inconveniences in handling in that an additional work is required for re-ordering the pages of the sheet material.
Further, the number of sortings available to the sheet material depends on the number of bins available. Increasing the number of sortings, therefore, requires an increased number of bins, thus disadvantageously increasing the size of the device.